From what I've read on various breeders' websites, most breed males at anywhere from 500-650grams without a whole lot of worry.

Its not about them 'giving up' any wieght in breeding effort per se, but more like if they do refuse food all season, will they have the body mass to handle the fast.

In your case, you shouldn't have any problems getting a male up to anywhere from 500 to even 1000 grams in 17 months. I've got a fall '05 male which currently weighs in at about 550 grams, and he's not the strongest feeder either.